Figure 2: Schematic illustration of the experimental protocol. Following intradermal injection of ET-1 on the forearm, responses to mechanical stimulation were tested after 10 and 30 min. Following acquisition of the anatomical scout, a block design was employed with two conditions (stimulus and baseline). Each stimulus block consisted of 12 blocks of tactile stimulation of the injection site alternated by as many blocks of contralateral (noninjected) arm stimulation. Both conditions were separated by a resting condition that consisted of no stimulation whatsoever. Each of the stimulation blocks lasted for 30 seconds.